Why cellulose over fiberglass?

In the world of insulation, seldom things are more heatedly debated than which type of insulation is better: fiberglass insulation or cellulose insulation. Both have their strengths and weaknesses, so let’s see what all the fuss is about. In order to fairly compare the two types of insulation, you have to consider all of the qualities the best insulation should do. This includes things like: Increase the level of energy efficiency of your home Reduce the risk of fire. Limit the amount of sound that passes through your walls and ceilings.

Increasing Energy Efficiency is such a vague concept. So, let’s cut to the chase and just say Energy Efficiency = Lower Utility Bills. Define the overall energy efficiency of your home with the amount you spend each month to keep your home at a comfortable temperature or your heating and cooling bills. After all, isn’t that the only thing that really matters? This is a better criterion to use than simply stating R-values because this is where the real differences between fiberglass and cellulose insulation are obvious. Although both types of insulation can offer similar r-values per inch, this only measures the insulation’s ability to reduce conductive heat transfer. Which only addresses heat passing through home’s building envelope if it’s undisturbed by air currents. In reality, the wind blows and heat rises creating convective heat loss. Which is heat carried through the air. Conductive heat loss accounts for a significant amount of energy consumed in the average U.S. home. Warm air currents passing through the walls, floors and ceilings in your home increase the amount of money you spend on energy bills. Reduced Air Leakage = Increased Energy Efficiency FIberglass insulation’s main drawback is its inability to block air from passing through it. This may not sound like a big deal until you realize that 20%+ of your heat or air conditioning can pass through the fiberglass insulation. Densely packed cellulose limits air movement and prevents drafts much better than fiberglass insulation. This is well documented by the University of Colorado in their evaluation of identical homes insulated with fiberglass and cellulose. The results of their study showed cellulose reduced air leakage by 38% and required 26% less money to heat and cool than the fiberglass home.

Fiberglass insulation gains its insulating power by trapping air inside of the billions of tiny glass fibers. The air trapped inside of the air pockets is what actually slows the transfer of heat through the space. Trying to create a continuous even layer of tiny air pockets with fiberglass insulation is extremely difficult. Mainly because fiberglass insulation comes in batts or rolls and must be cut to fit exactly into place. Wires, pipes, ducts and the wood framing itself always get in the way. So, the person installing the fiberglass insulation is basically assembling a massive jigsaw puzzle where each piece needs to be cut perfectly with a $3 utility knife. To make things even harder, the fiberglass insulation is thick and squishy. Cutting each piece to fit around all of the obstacles and tuck it neatly into position is slow and tedious. In real life, there’s just no time for this painstakingly slow process. So many fiberglass insulation installers completely disregard the obstacles and jam the insulation into place, hoping that the drywall with cover up their mistakes (which it always does). Jamming fiberglass insulation into a space compresses the insulation and squeezes out most of the air pockets. Without air pockets to slow down the heat, compressed fiberglass insulation does little more than fill the space with colorful fibers. The homeowner is left with a collection of holes and compressed insulation throughout their home sacrificing R-value, comfort and energy efficiency.

In contrast to fiberglass insulation, cellulose insulation does not trap air in between it’s fibers to control heat. By nature, the cells inside the cellulose insulation have their own insulating power. Which means cellulose insulation can be compressed into a space and offer additional r-value. Cellulose insulation is actually shredded paper with a fire retardant chemical known a borate. During the manufacturing process, this paper is broken down into its most basic element, cellular fibers from a tree. It’s these fibers that provide the insulating power for cellulose insulation. Installing the granular fibers that comprise cellulose insulation is done with a specialized machine known as an insulation blower. During the installation, the cellulose fibers flow through a long hose guided by the insulation contractor where it’s blown or sprayed into the space. Controls on the machine allow the installer to select the density of the insulation which enables them to densely pack it into a wall or floor cavity. Dense packing cellulose insulation into a wall or floor creates a continuous even layer of insulation. Pipes, wires, ductwork and electrical outlets are no problem for cellulose insulation because it is blown into the space is tiny pieces that fill in around the obstacles. The end result is usually much closer to our ideal insulation criteria from above. Cellulose insulation offers a more consistent, worry free installation when performed by a professional. Mainly because it completely fills the space between the framing by easily filling in around all of the obstacles, offers a slightly higher r-value per inch and will remain locked in place from the high pressure installation. Another important benefit from dense packed cellulose is its ability to limit air movement which cuts down on heat loss through convection. Another major weakness of fiberglass insulation which does nothing to stop air from passing through it.

The following is a summary of an extensive Natural Resources Defense Council (NRDC) report. The NRDC is a non-profit environmental membership organization with over 300,000 members and contributors nationwide: The NRDC has concluded the following:
• Cellulose insulation manufactured from recycled paper is the least polluting and most energy efficient insulation.
• Cellulose has the highest post-consumer recycled content. The fiberglass industry averages 35% recycled glass, while the cellulose industry averages a minimum of 75% recycled content.
• It takes more than 10 times as much energy to produce fiberglass insulation as cellulose insulation.
• Due to air circulation and natural convection, the R-value of blown-in fiberglass insulation decreases by as much as 50% as the temperature drops from 45 degrees F to 18 degrees F.
• Cellulose has better resistance to air flow and prevents the upward movement of air caused by temperature differences (the R-value of cellulose actually improves during cold weather).
• Substantial and well-documented public health threats are associated with fiberglass.
• No adverse health effects from cellulose insulation have been identified. Why Cellulose?
• Cellulose that has been properly installed in your walls will not settle.
• Cellulose is non-corrosive to steel, copper and aluminum.
• Cellulose will not lose it’s energy saving abilities over time.
• Cellulose will not rot, decay or mildew, and it does not support fungus or mold growth.

Why Cellulose?
• Cellulose that has been properly installed in your walls will not settle.
• Cellulose is non-corrosive to steel, copper and aluminum.
• Cellulose will not lose its energy saving abilities over time.
• Cellulose will not rot, decay or mildew, and it does not support fungus or mold growth.